1. Field of Invention
This invention relates to electrostatographic imaging devices.
2. Description of Related Art
Electrostatic reproduction and printing involves uniformly charging a photoconductive member, or photoreceptor, and imagewise discharging it, or imagewise exposing it, based on light reflected from, or otherwise representing, an original image being reproduced or printed. The result is an electrostatically-formed latent image on the photoconductive member. The latent image is developed by bringing a charged developer material into contact with the photoconductive member to form a toner powder image. The toner powder image is transferred to a receiving sheet and then fused by heating.
This process can be modified to form color images. One type of process, called image-on-image processing, superimposes toner powder images of different color toners onto the toner prior to the transfer of the composite toner powder image onto the substrate.
Two-component and single-component developer materials are known. Two-component developer materials comprise magnetic carrier particles and charged toner particles that adhere triboelectrically to the carrier particles and arc intended to adhere the photoconductive member.
Single-component developer material typically include only toner particles. The toner particles typically have an electrostatic charge to adhere to the photoconductive member, and magnetic properties to magnetically convey the toner particles from the sump to the developer roll. The toner particles adhere directly to the developer roll. The toner particles are attracted to the donor roll from a magnet or developer roll. From the donor roll, the toner is transferred to the photoconductive member in the development zone.
For both types of developer material, the charged toner particles are brought into contact with the latent image to form a toner image on the photoconductive member. The toner image is transferred to a receiver sheet, which passes through a fused device where the toner particles are heated and permanently fused to the sheet, forming a hard copy of the original image.
A development device is used to bring the charged toner particles into contact with the latent image formed on the photoreceptor, so that the toner particles adhere electrostatically to the charged areas on the latent image. The development device typically includes a chamber in which the developer material is mixed and charged.
One type of two-component development method and apparatus is known as "scavengeless development." "Hybrid" scavengeless development apparatus typically include a mixing chamber that holds a two-component developer material, at least one developer material developer or magnetic roll, a donor roll, a development zone, and an electrode structure at the development zone between the donor roll and the photoconductive member. The donor roll receives charged toner particles from the developer roll and transports the particles to the development zone. An AC voltage is applied to the electrodes to form a toner cloud in the development zone. Electrostatic fields generated by an adjacent latent image on the photoconductive member surface attract charged toner particles from the toner cloud to develop the latent image on the photoconductive member.
Another variation on scavengeless development uses single-component developer material development systems. As in two-component developer material development systems, the donor roll and electrodes also create a toner cloud.